Little Olaf has two piggy banks. Every day he puts one Euro in one of the banks until each bank
contains N Euros. Then he can buy a new toy.

Little Olaf also likes prime numbers. Sometimes, the amount of Euros in the first bank concatenated
with the amount of Euros in the second bank is a prime number. For example, if the first bank contains
12 Euros and the second bank contains 7 Euros, the concatenation 127 is a prime number.

Your task is to find an optimal order to put the Euros in the banks so that as many prime numbers as
possible appear. Initially, each bank contains 1 Euro.

Here is one order to fill the banks when N = 4:

1, 1 -> 2, 1 -> 2, 2 -> 3, 2 -> 3, 3 -> 4, 3 -> 4, 4

Only one prime number appears: 43. The following order is much better:

1, 1 -> 2, 1 -> 3, 1 -> 4, 1 -> 4, 2 -> 4, 3 -> 4, 4

Now three prime numbers appear: 31, 41, and 43. This is an optimal filling order for N = 4.

Note that the initial 11 is not counted!